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Programming in C (Part 2)

Here I will show you how to add and increment integer variables. Incrementation is shorthand code to increase or decrease (decrement) an integer variable by a certain amount.

#include &lt;stdio.h&gt;

void main()
{
int x, y;

x=5;

printf("The value of x is %i.\n",x);

x++;

printf("The value of x is now %i.",x);

y = x * 2 / 3;

printf("The value of y is %i.",y);

}

New code breakdown:

int x, y; - this tells the compiler to declare two integers at once. This saves you having to repeat the int declaration thing over and over again.

\n – When in a string, this tells the printf function to start a new line. This tidies up the output so it isn’t one big chunk of text.

x++; - this is a shorthand way of writing x = x + 1. It increases x by 1. It also has it’s opposite – x--. This (obviously) decreases x by 1.

y = x * 2 / 3; - the * bit here is the compilers way of writing a multiplication x. The forward slash is a division sign. Simple really. The compiler uses x to represent the value of x, obviously – in this case 6.

The output of this program should be:

The value of x is 5.
The value of x is now 6.
The value of y is 4.

Excellent.

5 – Characters and the getch() function

OK – so far we have only worked with numbers, but letters are also important. This program waits for a character to be pressed on the keyboard and prints it out.

#include stdio.h

void main()
{

char c;

c = getch();

printf(“You pressed the %c key”,c);

}

New code breakdown:

char c; - this declares a character variable. It uses an ASCII code to hold any of 256 characters.

c = getch(); - here, the getch() function is called, which waits for a keypress. When a key is pressed, the character that the key represents is ‘returned’ from the function and ‘passed’ by the = sign to the c variable. Got that?

%c – this tells the printf function to insert a character variable – similar to %i earlier.

6 – String variables

A string is a group of character variables – an ‘array’. This basically means that the characters are grouped in the computers memory and can be accessed by a single variable. It’s a little more complicated than that, but more will be explained in later lessons.

#include stdio.h

void main()
{

char string[] = “Wow! It’s a string!”;

printf(“%s, string);

}

New code breakdown:

char string[] – as I said earlier, a string is a group of characters. The [] brackets show that it is a group and not just a single variable.

string[] = “Wow! It’s a string!” – This is an example of initialising and declaring a variable on the same line. Again, it’s just a space saver.

%s – another symbol for the printf() function, this time specifying a string.